A single-crystal diamond has excellent properties such as high hardness, high thermal conductivity, and high light transmitting property, and has been therefore widely used for various products (hereinafter, also referred to as “diamond products”) such as tools, optical components, semiconductors, and electronic components. Examples of the tools include a cutting tool, a grinding tool, a wear resisting tool, and the like. For single-crystal diamonds used for such diamond products, natural diamonds and synthetic diamonds can be employed. The natural diamonds have large variation in quality and an amount of supply thereof is not stable. Hence, many synthetic diamonds are also used currently.
As one method of producing such a synthetic diamond, a high temperature high voltage method (HPHT) has been known. Single-crystal diamonds produced by this method has small variation in quality and an amount of supply thereof is stable; however, cost of a production facility used therefor is high, disadvantageously.
Moreover, as another method of producing a synthetic diamond, there are chemical vapor deposition (CVD) methods such as a hot filament CVD (Chemical Vapor Deposition) method, a microwave-excited plasma CVD method, and a DC plasma CVD method. In each of the CVD methods, a single-crystal diamond (epitaxial growth layer) is grown on a surface of a substrate, and then the substrate is separated from the single-crystal diamond. In this way, the single-crystal diamond can be obtained.
For example, Patent Document 1 (Japanese Patent Laying-Open No. 2013-35732) discloses a single-crystal diamond obtained by a vapor deposition method and a tool using the single-crystal diamond. In the single-crystal diamond, at least one or more conductive layers are formed substantially in parallel with a main surface thereof inside the insulative single-crystal diamond and extend to a side surface of the single-crystal diamond.